JP5207275B2 - Positive electrode active material for secondary battery, positive electrode for secondary battery and secondary battery using the same - Google Patents

Description

  The present invention relates to a positive electrode active material for a secondary battery, and is used for a lithium secondary battery or a lithium ion secondary battery with high capacity and improved charge / discharge characteristics, particularly cycle life at high temperature and capacity storage characteristics / self-discharge characteristics. The present invention relates to a positive electrode active material for a secondary battery.

  Lithium-ion secondary batteries are a composite oxidation of lithium and transition metal oxides with a negative electrode using a carbonaceous material that can be doped or dedoped with lithium, or a metal material that forms an alloy with lithium and lithium. A positive electrode using an active material as an active material is used. Each of the strip-like negative electrode side current collector and the positive electrode current collector, which is applied and laminated via a separator, is covered with an exterior material or laminated. A battery is manufactured by accommodating a wound body obtained by winding the product in a spiral shape in a battery can. As the positive electrode active material used for this positive electrode, a composite oxide of lithium and a transition metal such as lithium cobalt oxide and lithium nickel oxide is used.

  In particular, lithium manganese oxide is characterized by higher safety in an overcharged state or the like than lithium cobalt oxide, and moreover, manganese is richer in recoverable reserves than cobalt.

Lithium manganese oxide has a spinel structure represented by the chemical formula LiMn ₂ O ₄ and functions as a 4V-class positive electrode material between the composition and λ-MnO ₂ . Since spinel-structured martyungan oxide has a three-dimensional host structure that is different from the layered rock salt structure of lithium cobalt oxide, most of the theoretical capacity can be used and it is expected to have excellent cycle characteristics. The

  However, secondary batteries using lithium manganese oxide have a problem of capacity deterioration due to repeated charge / discharge cycles at high temperatures and a decrease in storage capacity due to self-discharge. In addition, a battery that requires a large current, such as power storage or an electric vehicle power source, is required to have a low resistance and a resistance that does not increase over a long period of time.

Therefore, there are many cases where characteristics are improved by replacing some constituent elements of lithium manganese oxide or using lithium manganese composite oxide in which the proportion of lithium is higher than that of LiMn2O4. Proposed.
Moreover, Mg, Al, Co, Ni, K, Na, Ca, Si, Fe, Cu, Zn, Ti, Sn, V, Ge, Ga, B, P, Se, Bi, As, and Zr are added to lithium manganese oxide. It has been proposed to introduce at least one element selected from Mn, Cr, Sr (for example, Patent Document 1).
However, characteristics such as cycle characteristics, high energy density, and increase rate of electrode resistance are not satisfactory.
JP 2003-331845 A

  In lithium ion batteries using lithium manganese composite oxide as the positive electrode, the lithium manganese oxide retains the characteristics such as thermal stability, has excellent battery characteristics, especially long-term high-temperature charge / discharge cycle characteristics, long-term storage characteristics, It is an object of the present invention to provide a non-aqueous electrolyte two battery with a small increase.

The present invention is represented by chemical formula 1: Li1 + xMn2-xyz-wAlyCozCawO4 ( 0.05 ≦ x <0.25, 0.01 <y <0.2, 0.01 <z <0.2, 0.005 ≦ w). <0.1, x + y + z + w <0.4) The positive electrode active material for a secondary battery including a calcium-aluminum-cobalt-containing lithium manganese composite oxide having a spinel structure and a secondary battery including a hydrogen ion scavenger It is a positive electrode.
Moreover, the said positive electrode for secondary batteries WHEREIN: The said hydrogen ion scavenger is a positive electrode for secondary batteries which is a lithium nickel complex oxide.
Further, in the positive electrode for a secondary battery described above, the lithium manganese composite oxide content in the positive electrode for a secondary battery is (100-a) parts by mass, and the lithium in the positive electrode for a secondary battery is When the content of the nickel composite oxide is a part by mass, the secondary battery positive electrode satisfies 3 <a ≦ 45.
A secondary battery comprising the positive electrode for a secondary battery according to any one of the above, an electrolyte, a separator, and a negative electrode disposed to face the positive electrode for a secondary battery via the electrolyte and the separator.
In the secondary battery, the electrolyte is a nonaqueous electrolyte containing a supporting salt containing LiPF ₆ or LiBF ₄ and an organic solvent.

A positive electrode active material for a secondary battery of the present invention Formula _{1: Li 1 + x Mn 2} -xyzw Al y Co z Ca w O 4 (0.03 <x <0.25,0.01 <y <0 .2, 0.01 <z <0.2, 0 <w <0.1, x + y + z + w <0.4), the calcium-aluminum-cobalt-containing lithium-manganese composite oxide is excessively doped with lithium. In addition, the crystal structure is stabilized by substitution with aluminum, cobalt, and calcium, and elution of manganese, reaction with the electrolyte, oxygen release, and the like are suppressed as compared with the conventional lithium-manganese composite oxide. It is possible to provide a battery with improved long-term cycle life and resistance increase rate under a high temperature environment. Further, when a hydrogen ion scavenger is included, the effect of the hydrogen ion scavenger lasts longer than the conventional non-aqueous electrolyte secondary battery and produces a synergistic effect.

The capacity deterioration accompanying the charge / discharge cycle of the positive electrode containing the lithium manganese composite oxide is caused by the fact that the average valence of Mn ions changes between trivalent and tetravalent as the lithium manganese composite oxide enters and exits lithium. -Teller distortion occurs in the crystal, manganese elution from lithium manganese composite oxide or impedance rise due to manganese elution, inactivation due to release of active material particles, and generation by moisture content The influence of the acid produced, deterioration of the electrolyte solution due to the release of oxygen from the lithium manganese composite oxide, and the like are considered.
Therefore, by substituting some of the constituent elements of the lithium manganese composite oxide, the characteristics of the lithium manganese composite oxide are maintained, and the charge / discharge characteristics, particularly the charge / discharge capacity, are improved. It has been found that charge / discharge cycle characteristics, long-term storage characteristics, and low resistance increase rate characteristics can be improved.

Positive electrode active material for a secondary battery of the present invention has the formula _{1: Li 1 + x Mn 2} -xyzw Al y Co z Ca w O 4 (0.03 <x <0.25,0.01 <y <0 .2, 0.01 <z <0.2, 0 <w <0.1, x + y + z + w <0.4), and a calcium aluminum cobalt-containing lithium manganese composite oxide.
In the compound of Chemical Formula 1, in the state before charge and discharge, lithium and cobalt that are excessively doped stabilize the crystal by lowering the lattice constant of the spinel structure, and aluminum has a stable trivalent oxidation degree. It is considered that the structure is stabilized by showing.
In addition, by replacing with cobalt and aluminum, it becomes possible to insert and desorb some of the excessively doped lithium stably during charging and discharging, and a lithium-manganese composite with a higher capacity than the conventional lithium excess composition. It is considered that an oxide can be obtained.
Furthermore, it is considered that by adding calcium showing a stable bivalent oxidation degree, the distortion of the crystal lattice accompanying the charge / discharge cycle was relaxed, and as a result, the cycle characteristics of the secondary battery could be improved. It is done.

In the calcium aluminum cobalt-containing lithium manganese composite oxide represented by Chemical Formula 1, x representing the amount of lithium present in excess is preferably 0.05 or more and less than 0.25. When x is smaller than 0.05, the storage capacity is significantly reduced due to self-discharge, which is not preferable. Moreover, when it is 0.25 or more, a sufficient charge / discharge capacity cannot be obtained, which is not preferable.
Further, y indicating the amount of aluminum substituted is preferably larger than 0.01 and smaller than 0.2. When y is 0.01 or less, the effect of substitution cannot be obtained, and when it is 0.2 or more, aluminum in the crystal structure is liberated as an aluminum compound such as aluminum oxide in the course of the charge / discharge cycle. Since electrode resistance is raised, it is not preferable.
In addition, if w indicating the amount of substituted calcium is less than 0.005, the effect of substitution is not obtained, and if it is 0.1 or more, calcium in the crystal structure is oxidized in the course of the charge / discharge cycle. It is not preferable because it is liberated as a calcium compound such as calcium and as a result the electrode resistance is increased.
Furthermore, when the sum of x + y + z + w is 0.4 or more, a stable crystal structure cannot be obtained, which is not preferable.

Next, the manufacturing method of the calcium aluminum cobalt containing lithium manganese complex oxide shown by Chemical formula 1 of this invention is demonstrated.
A compound containing each metal component of lithium, manganese, cobalt, aluminum, and calcium constituting Chemical Formula 1 is weighed and mixed so as to have a target metal composition ratio. The mixing can be performed by pulverization and mixing with a ball mill, a jet mill or the like. Next, the mixed powder is calcined in air or oxygen at a temperature of 600 ° C. to 950 ° C. to obtain a calcium aluminum cobalt-containing lithium manganese composite oxide of Formula 1.
The firing temperature is preferably a high temperature for diffusing each element, but if the firing temperature is too high, oxygen deficiency may occur, which may adversely affect battery characteristics. For this reason, it is preferable that a calcination temperature shall be about 650 degreeC to 850 degreeC.
Moreover, it can replace with using a solid raw material and can also manufacture by methods, such as a sol gel process and hydrothermal synthesis, using the liquid raw material containing each component.

Li ₂ CO ₃ , LiOH, Li ₂ O, Li ₂ SO _{4 and the} like can be used as the lithium raw material that can be used, and Li ₂ CO ₃ , LiOH, and the like are suitable.
As the manganese raw material, electrolytic manganese dioxide, chemically synthesized manganese dioxide, various manganese oxides such as Mn ₂ O ₃ and Mn ₃ O ₄ , MnCO ₃ , MnSO _{4 and the} like can be used. Examples of the cobalt raw material include CoO, Co ₃ O ₄ , CoCl ₂ , Co (OH) ₂ , CoSO ₄ , CoCO ₃ , and Co (NO ₃ ) ₂ .
Examples of the aluminum raw material include Al ₂ O ₃ , AlCl ₃ , Al (OH) ₃ , Al ₂ (SO ₄ ) ₃ , AlCO ₃ , and Al (NO ₃ ) ₃ .
Examples of the calcium raw material include CaO, Ca (OH) ₂ , CaCl ₂ , Ca (NO ₃ ) ₂ , and CaCO ₃ .

Manganese raw materials and substitutional element raw materials may hardly cause element diffusion during firing. After firing the raw materials, manganese oxides and substitutional element oxides may remain as different phases. In order to avoid such problems, cobalt raw material, manganese raw material, aluminum raw material, calcium raw material is dissolved and mixed in an aqueous solution, and then precipitated in the form of hydroxide, sulfate, carbonate, nitrate, etc. A compound, a manganese compound, an aluminum compound, a calcium compound, or a mixture of compounds containing these substitution elements may be used as a raw material.
Moreover, you may use the oxide obtained by baking these compounds, or its mixture in oxidizing atmosphere, or mixed oxide. In particular, mixed oxides that have been pre-mixed with the compound to form oxides have good dispersion of manganese, cobalt, aluminum, and calcium compounds, so the introduction of cobalt, aluminum, and calcium into the 16d site of the spinel structure is effective. Can be done automatically.

The specific surface area of the obtained calcium aluminum cobalt-containing lithium manganese composite oxide is preferably 1.5 m ² / g or less, more preferably 0.9 m ² / g or less. The larger the specific surface area, the more binder is required, which may be disadvantageous in terms of the capacity density of the positive electrode active material.

The nonaqueous electrolyte battery secondary battery of the present invention will be described below with reference to the drawings.
FIG. 1 is a cross-sectional view illustrating one embodiment of a non-aqueous electrolyte secondary battery.
The non-aqueous electrolyte secondary battery 1 is sealed by a battery outer case 2 made of a flexible outer material, and a battery element 3 is disposed inside the non-aqueous electrolyte secondary battery 1. The battery element 3 includes a positive electrode 4 in which a positive electrode active material-containing layer 12 is formed on a positive electrode current collector 11 and a negative electrode 5 in which a negative electrode active material-containing layer 14 is formed on a negative electrode current collector 13 through a separator 6. The battery element 3 is immersed in the nonaqueous electrolyte solution 7. The positive electrode 4 and the negative electrode 5 are connected to the positive terminal 8 and the negative terminal 9.

Hereinafter, one embodiment of the method for producing a battery of the present invention will be described.
Preparation of positive electrode Mixed with calcium aluminum cobalt-containing lithium-manganese composite oxide synthesized from an oxide of a specified blending ratio, with a conductivity-imparting material such as carbon black and a binder, and a dispersion medium containing a solvent capable of dissolving the binder To form a slurry.
As the conductivity imparting material, carbon black, acetylene black, natural graphite, artificial graphite, carbon fiber, or the like can be used. As the binder, polytetrafluoroethylene, polyvinylidene fluoride, or the like can be used.
Next, the slurry is applied on a current collector 11 such as aluminum or titanium to form the positive electrode active material-containing layer 12, and then the solvent is removed by drying, followed by compression with a roll or the like to obtain the positive electrode 4.

Production of Negative Electrode The negative electrode active material is made of a material that can occlude and release lithium, such as lithium metal or carbon material. As the carbon material, graphite that occludes lithium, amorphous carbon, diamond-like carbon, fullerene, carbon nanotube, carbon nanohorn, or a mixture thereof can be used.
In the case of a negative electrode active material made of a carbon material, a carbon material and a binder such as polyvinylidene fluoride are mixed, dispersed and kneaded in a solvent such as N-methyl-2-pyrrolidone, and this is mixed with copper foil or the like. After forming the coated negative electrode active material-containing layer 14 on the negative electrode current collector 13, the negative electrode 5 is obtained by drying and compressing with a roll or the like.

  Moreover, as the separator 6, a woven fabric, a nonwoven fabric, a porous film, etc. can be used. In particular, polypropylene and polyethylene-based porous films are preferable because they are thin and have a large area, film strength and film resistance.

  In addition, the nonaqueous electrolytic solution 7 is obtained by dissolving a supporting salt in a nonaqueous solvent. Solvents include cyclic carbonates such as propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate (BC), and vinylene carbonate (VC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC). ), Chain carbonates such as dipropyl carbonate (DPC), aliphatic carboxylic acid esters such as methyl formate, methyl acetate and ethyl propionate, γ-lactones such as γ-butyrolactone, 1,2-ethoxyethane ( DEE), chain ethers such as ethoxymethoxyethane (EME), cyclic ethers such as tetrahydrofuran and 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, acetamide, dimethylformua Imide, dioxolane, acetonitrile, propylnitrile, nitromethane, ethyl monoglyme, phosphoric acid triester, trimethoxymethane, dioxolane derivative, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, 3-methyl-2- Aprotic organic solvents such as oxazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethyl ether, 1,3-propane sultone, anisole, N-methylpyrrolidone, fluorinated carboxylic acid esters, etc. can be used singly or in combination. . Of these, propylene carbonate, ethylene carbonate, γ-butyl lactone, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate and the like are preferably used alone or in combination.

Examples of the supporting salt dissolved in these organic solvents include lithium salts. Examples of the lithium salt include LiPF ₆ , LiAsF ₆ , LiAlCl ₄ , LiClO ₄ , LiBF ₄ , LiSbF ₆ , LiCF ₃ SO ₃ , LiC ₄ F ₉ CO ₃ , LiC (CF ₃ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiB ₁₀ Cl ₁₀ , lower aliphatic carboxylic acid lithium carboxylate, lithium chloroborane, lithium tetraphenylborate, LiBr, LiI, LiSCN, LiCl, imides, etc. can give. Further, a polymer electrolyte may be used instead of the electrolytic solution. The electrolyte concentration is, for example, 0.5 mol / l to 1.5 mol / l. If the concentration is too high, density and viscosity increase. If the concentration is too low, the electrical conductivity may decrease.

The non-aqueous electrolyte secondary battery of the present invention comprises a battery element 3 in which a positive electrode 4 and a negative electrode 5 are laminated via a separator 6 in a dry air, nitrogen, or inert gas atmosphere. It is obtained by sealing and impregnating the electrolytic solution 7 and then sealing the battery outer container 2.
Although the example using the battery element in which the positive electrode and the negative electrode are laminated via the separator has been described with reference to FIG. 1, the belt-shaped positive electrode and the negative electrode may be wound around the separator. . Moreover, not only the thing using the flexible exterior film which laminated the polyethylene film, the polypropylene film, the polyamide film, the polyester film etc. on both surfaces of metal foils, such as aluminum foil, but a coin type, a square type, a cylindrical type, etc. Various shapes can be used.

In addition to the calcium aluminum cobalt-containing lithium manganese composite oxide of the present invention, the positive electrode for a non-aqueous electrolyte secondary battery of the present invention captures hydrogen ions generated by the reaction between the water in the electrolyte and the electrolyte. The lithium nickel composite oxide described in Japanese Patent No. 2996234 having an action as a hydrogen ion scavenger may be contained.
Since the lithium nickel composite oxide added as a hydrogen scavenger functions as a positive electrode active material, even if the amount of the calcium aluminum cobalt-containing lithium manganese composite oxide of the present invention decreases due to the addition of the hydrogen scavenger, lithium Since the nickel composite oxide serves as a positive electrode active material, a decrease in capacity can be prevented.
In particular, when the lithium nickel cobalt composite oxide represented by LiNi _0.8 Co _0.2 O ₂ is combined with the positive electrode active material of the present invention as a hydrogen scavenger of the present invention, a characteristic improvement effect can be obtained synergistically. When mix | blending lithium nickel cobalt complex oxide, it is preferable to add 3 mass parts or more of the whole quantity of complex oxide in a positive electrode.

  Due to the presence of such a hydrogen ion scavenger, various actions such as reducing the concentration of hydrogen ions in the secondary battery occur, and the decomposition and deterioration of the electrolyte are suppressed. As a result, the secondary battery is cycled at high temperatures. It is considered that the life and capacity storage characteristics, low resistance characteristics, and low resistance increase characteristics can be improved.

The present invention will be described below with reference to examples and comparative examples of the present invention.
Example 1
Synthesis of Lithium Manganese Metal-Substituted Composite Oxide Lithium Carbonate (Li ₂ CO ₃ ) Ground and Classified to a Number Average Particle Size of 5 μm, and Manganese Oxide, Cobalt Oxide, Aluminum Hydroxide, Water, Ground and Classified to a Number Average Particle Size of 10 μm Calcium oxide was prepared at a predetermined ratio and mixed for 2 hours by a planetary ball mill, and the obtained mixture was put in a crucible and subjected to primary firing at 800 ° C. in air. Next, the primary fired product was crushed and remixed, followed by secondary firing in air at 600 ° C.

  Next, the obtained fired product was pulverized using a pulverizer (Ishikawa stirring lightning pulverizer), so that in Table 1, the values of x, y, z, and w in Chemical Formula 1 and the respective chemical formulas are shown. The calcium aluminum cobalt-containing lithium manganese composite oxide represented by Chemical Formula 1 of Samples 1 to 9 having a spinel structure and a number average particle size of 10 μm, and Comparative Materials 1-9 were obtained.

Further, the obtained powdery composite oxide was subjected to X-ray diffraction measurement using CuKα rays. FIG. 2 shows the X-ray diffraction pattern of the calcium aluminum cobalt-containing lithium manganese composite oxide used as the positive electrode active material of Sample 1 and the results of the same measurement for LiMn ₂ O ₄ (manufactured by Toda Kogyo Co., Ltd.) for comparison. FIG.
Further, as shown in FIG. 2, a diffraction pattern that can be indexed in the space group R-3m is obtained, and as a result of comparison with JCPDS (# 35-782), the synthesized powder has a spinel structure. It was confirmed. As a result of detailed verification, it was confirmed that no heterogeneous phase was observed in the synthesized powder. Further, X-ray diffraction measurement was performed in the same manner for Sample 2 to Sample 9 and Comparative Sample 1 to Comparative Sample 13, and it was confirmed that the synthesized powder had a spinel structure and no heterogeneous phase was observed.

Manganese dissolution test 5 ml of the obtained sample or comparative sample and 10 ml of an electrolyte solution having a volume ratio of 50:50 of propylene carbonate and dimethyl carbonate containing LiPF ₆ at a concentration of 1 mol / L were placed in a sealed container. Next, Table 2 shows the results of analyzing the manganese concentration eluted in the electrolytic solution by ICP emission spectroscopic analysis after holding each sealed container in a thermostat heated to 80 ° C. for 20 days.

Preparation of Battery A composite oxide of the chemical formula 1 of Sample 1 and carbon black as a conductivity-imparting agent are dry-mixed and uniformly dispersed in N-methyl-2-pyrrolidone in which vinylidene fluoride is dissolved as a binder. Produced.
The obtained slurry was applied onto an aluminum foil having a thickness of 20 μm and then dried to remove the solvent to obtain a positive electrode having a thickness of 88 μm. The solid content ratio in the positive electrode was a mass ratio, and was positive electrode active material: conductivity imparting agent: PVDF = 89: 4: 7.

  On the other hand, graphite: PVDF = 90: 10 (mass ratio) was mixed and dispersed in N-methyl-2-pyrrolidone, and applied onto a 10 μm thick copper foil to prepare a 49 μm thick negative electrode. An electrolyte solution having a volume ratio of 50:50 of propylene carbonate and dimethyl carbonate containing LiPF6 at a concentration of 1 mol / L, which is formed by laminating and winding a negative electrode and a positive electrode through a separator made of polyethylene and storing them in a cylindrical container. The sample battery 1 to the test battery 9 and the comparative test battery 1 to the comparative test battery 9 were produced.

High-temperature cycle characteristics Each of the obtained test batteries and comparative test batteries at a temperature of 65 ° C. under the conditions of a charge rate of 1.0 C and a charge end voltage of 4.3 V, the battery voltage reached 4.3 V, and then the constant voltage charge was 1 After 5 hours of charging, a charge / discharge test was conducted to discharge at a discharge rate of 1.0 C up to a final discharge voltage of 2.5 V, and the discharge capacity (mAh) at the 100th cycle relative to the discharge capacity (mAh) at the 10th cycle. The ratio is shown in Table 2 as a percentage of capacity retention.
At the same time, the theoretical discharge capacity per 1 g (mAh) calculated from the change in the valence of manganese in the positive electrode active material is shown.

Example 2
Table 3 shows the results of measuring the change in internal DC resistance of the secondary batteries for testing produced in Example 1 by the following evaluation method.
Measurement of internal DC resistance At a temperature of 20 ° C., the battery was charged to 4.3 V at a charge rate of 0.5 C. After reaching 4.3 V, constant voltage charging was performed for 2 hours for charging. The discharged battery was discharged at 0.1 C to a discharge depth of 50%, and then the voltage when discharged at a discharge rate of 1 C for 10 seconds was measured.

Subsequently, after being allowed to stand for 10 minutes, the voltage when charged at a 3C charging rate for 10 seconds was measured. Further, the voltage was measured when the battery was discharged for 10 seconds at a discharge rate of 5 C after being left for 10 minutes, and the voltage was measured when the battery was charged again for 10 seconds at a charge rate of 3 C after being left again for 10 minutes.
Thereafter, at 10-minute intervals, the charge / discharge rate was set to 7C and 10C, and the same measurement was repeated to obtain a current-voltage straight line. The slope of this straight line was defined as the initial internal DC resistance. Moreover, after adjusting the test battery after measuring internal resistance to the state of 60% of the depth of discharge, it preserve | saved for four weeks in a 55 degreeC thermostat. Thereafter, the internal DC resistance measurement after storage of the internal DC resistance was performed in the same manner as described above, and the ratio of the internal DC resistance measurement after storage and the initial internal DC resistance was shown in Table 3 as the rate of increase in resistance.

From the above test results, as shown in Samples 1 to 9 of the present invention, a composite oxide in which lithium is excessive and aluminum, cobalt, and calcium are substituted has aluminum, cobalt, and Compared to a test battery using one in which either calcium is not substituted, the capacity retention rate and manganese elution amount are excellent.
This is because, when a part of manganese in the lithium manganese composite oxide is simultaneously replaced with four elements of aluminum, cobalt, and calcium, the excess lithium and cobalt stabilize the crystal by lowering the lattice constant of the spinel structure. The structure of aluminum is stabilized by showing a trivalent stable oxidation degree, and calcium showing a stable bivalent oxidation degree relaxes the distortion of the crystal lattice accompanying the charge / discharge cycle. For this reason, it is considered that the capacity retention rate was higher than that of the conventional lithium manganese composite oxide composition, and excellent effects were obtained in the elution amount of manganese and the resistance increase rate.

Example 3
The test battery 1 was tested in the same manner as in Example 1 except that a part of the sample 1 used as the positive electrode active material was replaced with LiNi _0.8 Co _0.2 O ₂ , which is a lithium nickel cobalt composite oxide, by changing the blending ratio. Batteries 10 to 15 were produced.
Further, in the comparative test battery 1, Example 1 except that a part of the comparative sample 1 used as the positive electrode active material was replaced with LiNi _0.8 Co _0.2 O ₂ which is a lithium nickel cobalt composite oxide while changing the mixing ratio. Similarly, comparative test batteries 14 to 19 were produced.
Further, in the test battery 1, except that a part of the sample 1 used as the positive electrode active material was replaced with LiCoO ₂ , which is a lithium cobalt oxide having no effect as a hydrogen ion scavenger, by changing the blending ratio. Comparative batteries 20 to 25 were produced in the same manner as in Example 1.
A charge / discharge test was performed in the same manner as in Example 1 to measure the capacity retention rate after 1000 cycles, and the sample 1 or the comparative sample 1 was mixed with the sample 1 or the comparative sample 1 of the lithium nickel cobalt composite oxide. The mass ratio to the total amount is shown in Table 4 and Table 5 in percentage.
Moreover, the high-temperature cycle test result in 65 degreeC about the test battery 13 and the comparison test battery 13 is shown in FIG.

Since the calcium-aluminum-cobalt-containing lithium-manganese composite oxide of the present invention has suppressed elution of manganese, the effect of LiNi _0.8 Co _0.2 O ₂ blended as a hydrogen ion scavenger is more pronounced. Conceivable.

  Lithium overdoping and the addition of aluminum, cobalt, and calcium stabilize the crystal structure and make it a lithium manganese composite oxide. Thus, it is possible to provide a battery which is suppressed more than a product and has improved long-term cycle life and resistance increase rate under a high temperature environment.

FIG. 1 is a diagram illustrating an embodiment of a non-aqueous electrolyte secondary battery. It is a figure explaining the X-ray-diffraction pattern of the positive electrode active material for secondary batteries of this invention. It is a figure which shows the cycle characteristic comparison of the discharge capacity in 60 degreeC of this invention and a prior art example.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Nonaqueous electrolyte secondary battery, 2 ... Battery exterior container, 3 ... Battery element, 4 ... Positive electrode, 5 ... Negative electrode, 6 ... Separator, 7 ... Nonaqueous electrolyte, 8 ... Positive electrode terminal, 9 ... Negative electrode Terminal, 11 ... Positive electrode current collector, 12 ... Positive electrode active material-containing layer, 13 ... Negative electrode current collector, 14 ... Negative electrode active material-containing layer

Claims (5)

Chemical formula 1: Li1 + xMn2-xyz-wAlyCozCawO4 ( 0.05 ≦ x <0.25, 0.01 <y <0.2, 0.01 <z <0.2, 0.005 ≦ w <0.1 X + y + z + w <0.4) A secondary battery comprising a positive active material for a secondary battery including a calcium-aluminum-cobalt-containing lithium-manganese composite oxide having a spinel structure , and a hydrogen ion scavenger. Positive electrode. 2. The positive electrode for a secondary battery according to claim 1 , wherein the hydrogen ion scavenger is a lithium nickel composite oxide. The positive electrode for a secondary battery according to claim 2 , wherein the content of the lithium manganese composite oxide in the positive electrode for the secondary battery is (100-a) parts by mass, and the lithium in the positive electrode for the secondary battery A positive electrode for a secondary battery, wherein 3 <a ≦ 45 is satisfied when the content of the nickel composite oxide is a part by mass. A positive electrode for a secondary battery according to any one of claims 1 to 3 , an electrolyte, a separator, and a negative electrode disposed opposite to the positive electrode for a secondary battery via the electrolyte and the separator. Secondary battery. 5. The secondary battery according to claim 4 , wherein the electrolyte is a nonaqueous electrolyte containing a supporting salt containing LiPF ₆ or LiBF ₄ and an organic solvent.

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